What is half diminished 7th chord?

A half diminished 7th chord, also known as a minor 7 flat 5 chord, is a four-note chord made up of a root note, a minor third, a diminished fifth, and a minor seventh. It is symbolized as "ø" or "m7b5."

The structure of a half diminished 7th chord is similar to a diminished chord but with a minor 7th added on top. It has a tense and somewhat dissonant sound, making it a popular choice for adding tension and color to jazz, classical, and other genres of music.

The half diminished 7th chord is commonly used as the ii chord in a minor ii-V-i progression, where it resolves to a minor i chord. It can also function as a dominant chord substitute or as a passing chord in a progression.

Overall, the half diminished 7th chord has a unique and complex sound that can add depth and richness to your musical compositions.